Tanzanite: Kilimanjaro's Gem

26th March 2020

Initially called the blue zoisite, this intense blue stone was christened by Tiffany & Co as tanzanite to refer to its sources and have a more appealing and exotic name.

Only found at the foot of the Kilimanjaro Mount in Tanzania, this gem has been discovered quite recently and is said to be the most beautiful blue stone found in the past 2000 years (Tiffany). The mining started in 1967 and, in only a few decades, tanzanite gained a global fame and already sees its sources come to an end due to its limited location. Indeed, tanzanite is rarer than diamond, however its value is much lower because of a lack of demand.

Different Rough Tanzanite Stones.

Thanks to its striking blue color, tanzanite is an interesting economic alternative to sapphire. However, its hues are slightly different than the blue precious stone: it reproduces the colors of the nightfall sky, from blue to purple and violet. This color is due to the presence of vanadium in the zoisite’s composition.

The more saturated is the blue color, the more valuable is the stone. Usually the hue is more intense when the stone is bigger than 5 carats as it tends to present a fade color when smaller. It is not rare to find important carat-weight tanzanite up to 50 carats and, today, the biggest rough stone discovered reaches 16’839 carats.

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Baroque Tanzanite Pendant, Moussaieff

63.60 cts Tanzanite, Diamonds

Tanzanite does not appear under one specific cut, but the aim is to emphasize the pleochroism of the stone. This physical property indicates that the gem can display 3 different colors depending on the crystal perspectives. It may reflects dark purple-blue from one side, violet-red from another, and blue-green from a third point. The lapidary needs to analyze the best angles and sides of the stone in order to enhance this spectacular effect.
80% of the sourced tanzanite show a brownish tint, which is why the majority of the stones offered on the market are often heated to enhance their blue tone.

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Pleochroism: same rough tanzanite stone seen from two different angles. 

Most of the time, tanzanite has a transparent body and does not present inclusions that are visible to the eye, in case it does, it will negatively affect its value. It reaches 6.5 on Mohs’ scale which indicates a pretty low resistance to scratches, especially compared to sapphire (9). Tanzanite is the modern December’s birthstone alongside with zircon and turquoise.

Tanzanite is rather widely used in jewellery and was well promoted by Tiffany & Co. The American jeweller chooses this purple blue stone as an alternative to sapphire to offer more accessible jewels such as the Paper Flowers collection. In 2012, Tiffany also raised tanzanite awareness with this unique necklace composed of a major center stone of 178.07cts, created at the occasion of the brand’s 175th Anniversary.

Tanzanite Jewels, Tiffany & Co. Legends on the pictures.

Cartier, Chopard, Bulgari, Van Cleef & Arpels, Louis Vuitton and other international jewelers also highlighted the energy blue stone in their creations.

Tanzanite Jewels. Legends on pictures.